Introduce setting for a max height level for towns

Prior to this change, the game tended to place towns on mountain tops. Realistic heightmaps had limitations because of this.

This change allows the player to specify that the towns should be generated in the valleys.

src/lang/english.txt

@@ -1918,6 +1918,8 @@ STR_CONFIG_SETTING_TOWN_CARGO_FACTOR                            :Town cargo gene
 STR_CONFIG_SETTING_TOWN_CARGO_FACTOR_HELPTEXT                   :Passenger, mail, and other town cargo production is scaled by approximately 2^factor (exponential)
 STR_CONFIG_SETTING_INDUSTRY_CARGO_FACTOR                        :Industry cargo generation factor (less < 0 < more): {STRING2}
 STR_CONFIG_SETTING_INDUSTRY_CARGO_FACTOR_HELPTEXT               :Primary industry cargo production is scaled by approximately 2^factor (exponential). This excludes tree-cutting industries.{}This is not guaranteed to be fully compatible with all industry NewGRFs.
+STR_CONFIG_SETTING_TOWN_ABOVE_HEIGHT                            :No towns above height level: {STRING2}
+STR_CONFIG_SETTING_TOWN_ABOVE_HEIGHT_HELPTEXT                   :No towns above the specified height level are built during map creation.
 
 STR_CONFIG_SETTING_EXTRA_TREE_PLACEMENT                         :In game placement of trees: {STRING2}
 STR_CONFIG_SETTING_EXTRA_TREE_PLACEMENT_HELPTEXT                :Control random appearance of trees during the game. This might affect industries which rely on tree growth, for example lumber mills

src/settings_gui.cpp

@@ -2036,6 +2036,7 @@ static SettingsContainer &GetSettingsTree()
 			genworld->Add(new SettingEntry("economy.initial_city_size"));
 			genworld->Add(new SettingEntry("economy.town_layout"));
 			genworld->Add(new SettingEntry("economy.town_min_distance"));
+			genworld->Add(new SettingEntry("economy.max_town_heightlevel"));
 			genworld->Add(new SettingEntry("difficulty.industry_density"));
 			genworld->Add(new SettingEntry("gui.pause_on_newgame"));
 			genworld->Add(new SettingEntry("game_creation.ending_year"));

src/settings_type.h

@@ -633,6 +633,7 @@ struct EconomySettings {
 	TownCargoGenMode town_cargogen_mode;     ///< algorithm for generating cargo from houses, @see TownCargoGenMode
 	bool   allow_town_roads;                 ///< towns are allowed to build roads (always allowed when generating world / in SE)
 	uint16  town_min_distance;               ///< minimum distance between towns
+	uint8  max_town_heightlevel;             ///< maximum height level for towns
 	TownFounding found_town;                 ///< town founding.
 	bool   station_noise_level;              ///< build new airports when the town noise level is still within accepted limits
 	uint16 town_noise_population[3];         ///< population to base decision on noise evaluation (@see town_council_tolerance)

src/table/settings.ini

@@ -939,10 +939,24 @@ strhelp  = STR_CONFIG_SETTING_TOWN_CARGOGENMODE_HELPTEXT
 strval   = STR_CONFIG_SETTING_TOWN_CARGOGENMODE_ORIGINAL
 cat      = SC_ADVANCED
 
-;; economy.max_town_heightlevel
-[SDT_NULL]
-length   = 1
+[SDT_XREF]
 extver   = SlXvFeatureTest(XSLFTO_AND, XSLFI_JOKERPP)
+xref     = ""economy.max_town_heightlevel""
+
+[SDT_VAR]
+base     = GameSettings
+var      = economy.max_town_heightlevel
+type     = SLE_UINT8
+guiflags = SGF_NEWGAME_ONLY | SGF_SCENEDIT_TOO
+def      = MAX_MAP_HEIGHT_LIMIT
+min      = 4
+max      = MAX_MAP_HEIGHT_LIMIT
+interval = 1
+str      = STR_CONFIG_SETTING_TOWN_ABOVE_HEIGHT
+strhelp  = STR_CONFIG_SETTING_TOWN_ABOVE_HEIGHT_HELPTEXT
+strval   = STR_JUST_INT
+cat      = SC_BASIC
+patxname = ""max_town_heightlevel.economy.max_town_heightlevel""
 
 ; link graph
 

src/town_cmd.cpp

@@ -2118,6 +2118,11 @@ static CommandCost TownCanBePlacedHere(TileIndex tile)
 		return_cmd_error(STR_ERROR_TOO_CLOSE_TO_ANOTHER_TOWN);
 	}
 
+	/* Check max height level. */
+	if (GetTileZ(tile) > _settings_game.economy.max_town_heightlevel) {
+		return_cmd_error(STR_ERROR_SITE_UNSUITABLE);
+	}
+
 	/* Can only build on clear flat areas, possibly with trees. */
 	if ((!IsTileType(tile, MP_CLEAR) && !IsTileType(tile, MP_TREES)) || !IsTileFlat(tile)) {
 		return_cmd_error(STR_ERROR_SITE_UNSUITABLE);